Static mechanical properties of the trachea and bronchial tree

Powell, William R.

doi:10.1016/0021-9290(75)90091-3

Cited by 10 publications

(7 citation statements)

References 9 publications

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“…1, where t 0 is the thickness of the airway wall at the baseline diameter D 0 . According to measurements made by Powell in isolated dog lungs (24), this ratio is typically greater than 6, validating the thin wall assumption. We can define the principal stretch ratios for changes in length (l z 5 L/L 0 ), circumference (l u 5 D/D 0 ), and thickness (l t 5 t/t 0 ), and due to incompressibility, l z l u l t 5 1.…”

Section: Limitations Of the Experimental Modelmentioning

confidence: 99%

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Airway Strain during Mechanical Ventilation in an Intact Animal Model

Sinclair

Molthen

Haworth

et al. 2007

Am J Respir Crit Care Med

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Rationale: Mechanical ventilation with large tidal volumes causes ventilator-induced lung injury in animal models. Little direct evidence exists regarding the deformation of airways in vivo during mechanical ventilation, or in the presence of positive end-expiratory pressure (PEEP). Objectives: To measure airway strain and to estimate airway wall tension during mechanical ventilation in an intact animal model. Methods: Sprague-Dawley rats were anesthetized and mechanically ventilated with tidal volumes of 6, 12, and 25 cm 3 /kg with and without 10-cm H 2 O PEEP. Real-time tantalum bronchograms were obtained for each condition, using microfocal X-ray imaging. Images were used to calculate circumferential and longitudinal airway strains, and on the basis of a simplified mathematical model we estimated airway wall tensions. Measurements and Main Results: Circumferential and longitudinal airway strains increased with increasing tidal volume. Levels of mechanical strain were heterogeneous throughout the bronchial tree. Circumferential strains were higher in smaller airways (less than 800 mm). Airway size did not influence longitudinal strain. When PEEP was applied, wall tensions increased more rapidly than did strain levels, suggesting that a ''strain limit'' had been reached. Airway collapse was not observed under any experimental condition. Conclusions: Mechanical ventilation results in significant airway mechanical strain that is heterogeneously distributed in the uninjured lung. The magnitude of circumferential but not axial strain varies with airway diameter. Airways exhibit a ''strain limit'' above which an abrupt dramatic rise in wall tension is observed.

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Section: Limitations Of the Experimental Modelmentioning

confidence: 99%

“…To approximate the stress distribution in the airways, we assumed the airways to be thin-walled cylinders and followed the analysis of Powell (24) and Green and Adkins (25). The circumferential wall tension is given by T u 5s u 3t 0 5ð1=2ÞD 0 Pl z l 2 u ð3Þ and longitudinal wall tension by…”

Section: Airway Strain and Tension Calculationsmentioning

confidence: 99%

Airway Strain during Mechanical Ventilation in an Intact Animal Model

Sinclair

Molthen

Haworth

et al. 2007

Am J Respir Crit Care Med

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“…To further define the elastic properties of bio logical tissues, concepts of engineering me chanics have been applied to both airways [4] and the lungs [5]. The elastic constants frequently utilized are the Bulk and the Young's modulus.…”

Section: Introductionmentioning

confidence: 99%

Effect of Intermittent Positive Pressure Application on the Bulk Modulus of the Developing Rabbit Trachea

Bhutani¹,

Shaffer²

1981

Respiration

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Tracheal dimension, pressure-volume relationships and bulk modulus (K) were determined in excised fetal and adult rabbit tracheal segments before and after application of intermittent positive pressure (IPP) which was 0–25 cm H₂O pressure, at 30 cycles/min, and for a duration of 60 min. Both tracheal elastic behavior and dimensions underwent dramatic changes following IPP. At 21, 27, 31 days gestation age, the bulk modulus, K, of the rabbit trachea approximated those of the adult control values. However, the adult values of K did not vary significantly after IPP. The associated increase in tracheal dimensions were also related to the maturity of the animal. Significant structural and functional barotrauma is thus sustained by immature airways, and may account for the tracheal deformation frequently observed as a result of IPP.

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“…The trachea has been previously mo delled as a homogeneous, isotropic struc ture: a reasonable compromise between theo retical exactness and analytical complexity [5]. The concept of engineering mechanics has been applied to adult canine tracheal [5] and lung parenchyma [6] preparations to determine their material properties or elas tic constants such as the bulk modulus.…”

Section: Introductionmentioning

confidence: 99%

“…The concept of engineering mechanics has been applied to adult canine tracheal [5] and lung parenchyma [6] preparations to determine their material properties or elas tic constants such as the bulk modulus. It has been suggested that these data quanti tate the nonuniform deformation of lung tis sue, beyond that obtained from pressurevolume relationships.…”

Section: Introductionmentioning

confidence: 99%

Alterations in Bulk Modulus of Tracheae during Development

Shaffer¹,

Bhutani²

1980

Respiration

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Tracheal dimensions, pressure-volume relationships, and bulk moduli, K, were determined in excised tracheae at different developmental ages: 21-, 27-, and 31-day rabbit fetuses; 7-day pups; and adult rabbits 18 ± 6 months of age. Alterations in tracheal dimensions paralleled the growth of the animal. At low segmental pressures such as 10 cm H₂O, the tracheal segments became stiffer with age (K = 20.4 cm H₂O for the 21-day fetus to K = 58.0 cm H₂O for the adult). However, at segmental pressures greater than 15 cm H₂O, the overdistended immature trachea became stiffer than even those of the adults. Developmental alterations in bulk modulus suggest significant changes in the material and mechanical properties of the airways as a function of both pressure and developmental age

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Static mechanical properties of the trachea and bronchial tree

Cited by 10 publications

References 9 publications

Airway Strain during Mechanical Ventilation in an Intact Animal Model

Airway Strain during Mechanical Ventilation in an Intact Animal Model

Effect of Intermittent Positive Pressure Application on the Bulk Modulus of the Developing Rabbit Trachea

Alterations in Bulk Modulus of Tracheae during Development

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